Gulf of Maine Seasonal Sea Surface Temperature Update
Seasonal Patterns in Sea Surface Temperatures
Winter 2024 Highlights
For this seasonal report we present an analysis of SST for winter (December 1, 2023 - February 28, 2024).
Winter is an important time of year for the Gulf of Maine. During this time of year sea surface temperatures are typically falling, and the surface stratification breaks down. The breakdown of stratification allows for vertical mixing in the water column, which helps transport important nutrients through the near-surface waters. These nutrients are what fuel the spring phytoplankton blooms that support the high productivity in the region. Vertical mixing may be enhanced in Winter with the help of Nor’Easters, which are most common this time of year and stir up the water column with rough seas and strong winds.
This year, the average SST for the Gulf of Maine was 43.35°F, making it the 23rd hottest winter on record for the period of 1982-2023 — the period over which the satellite data used are available.
This seasonal average temperature is -0.71°F above the 1991–2020 climatological reference period (CRP) winter average of 44.06°F.
Weekly Temperatures
Table 1 highlights how the SST for each week this winter compares to the 1991-2020 CRP for the area shown in Figure 8. The observed SST, long-term average SST, and SST anomalies (i.e., departures from the long-term average SST) are shown.
winter average SST was on average -0.71°F or more above normal during the fall, with weekly averaged SST anomalies ranging from -1.7°F to +0.4°F.
| Table 1. Weekly Average Sea Surface Temperatures - Winter | |||
| (December 1, 2023 - February 28, 2024) | |||
| One-Week Period | Observed Temperature | Climatological Average | Temperature Anomaly |
|---|---|---|---|
Dec 01 - Dec 02 |
49.3°F (9.6°C) |
49.4°F (9.7°C) |
-0.1°F (-0.1°C) |
Dec 03 - Dec 09 |
48.3°F (9.1°C) |
48.8°F (9.3°C) |
-0.4°F (-0.2°C) |
Dec 10 - Dec 16 |
47.4°F (8.5°C) |
47.8°F (8.8°C) |
-0.5°F (-0.3°C) |
Dec 17 - Dec 23 |
46.7°F (8.2°C) |
46.9°F (8.3°C) |
-0.2°F (-0.1°C) |
Dec 24 - Dec 30 |
46.4°F (8.0°C) |
45.9°F (7.8°C) |
0.4°F (0.2°C) |
Dec 31 - Jan 06 |
45.0°F (7.2°C) |
45.1°F (7.2°C) |
-0.0°F (-0.0°C) |
Jan 07 - Jan 13 |
43.8°F (6.6°C) |
44.2°F (6.8°C) |
-0.4°F (-0.2°C) |
Jan 14 - Jan 20 |
42.1°F (5.6°C) |
43.4°F (6.3°C) |
-1.2°F (-0.7°C) |
Jan 21 - Jan 27 |
40.9°F (5.0°C) |
42.6°F (5.9°C) |
-1.7°F (-0.9°C) |
Jan 28 - Feb 03 |
40.9°F (4.9°C) |
42.0°F (5.5°C) |
-1.1°F (-0.6°C) |
Feb 04 - Feb 10 |
40.4°F (4.7°C) |
41.4°F (5.2°C) |
-1.0°F (-0.6°C) |
Feb 11 - Feb 17 |
40.0°F (4.5°C) |
40.9°F (4.9°C) |
-0.9°F (-0.5°C) |
Feb 18 - Feb 24 |
39.2°F (4.0°C) |
40.5°F (4.7°C) |
-1.3°F (-0.7°C) |
Feb 25 - Feb 28 |
38.8°F (3.8°C) |
40.2°F (4.6°C) |
-1.5°F (-0.8°C) |
| Data Source: NOAA OISSTv2 Daily Sea Surface Temperature Data. | |||
| Climatological Reference Period: 1991-2020. | |||
Monthly Statistics
Table 2 shows monthly average SST for winter 2024; each month was within -1°F or more above the 1991-2020 CRP.
February showed the largest deviation from the long-term climatological average, with an average SST anomaly of -1.08 °F, making it the 34th warmest February` on record.
December and January were warmer at -0.1 & 0.9°F below the long-term average—coming in as the 19th and 25th warmest December and January on record, respectively.
| Table 2. Monthly Average Sea Surface Temperatures - Winter | ||||
| (December 1, 2023 - February 28, 2024) | ||||
| Month | Rank (1982-2023) | Observed Temperature | Climatological Average | Temperature Anomaly |
|---|---|---|---|---|
December |
19 |
47.3°F (8.5°C) |
47.4°F (8.6°C) |
-0.1°F (-0.1°C) |
January |
25 |
42.6°F (5.9°C) |
43.5°F (6.4°C) |
-0.9°F (-0.5°C) |
February |
34 |
39.8°F (4.3°C) |
40.9°F (5.0°C) |
-1.1°F (-0.6°C) |
| Data Source: NOAA OISSTv2 Daily Sea Surface Temperature Data. | ||||
| Climatological Reference Period: 1991-2020. | ||||
How Does this Winter Compare to the Past?
2024 was the 23rd warmest winter season observed in the Gulf of Maine during the 41 years we have satellite data to analyze, a departure winter seasons in recent years, which experienced well-above average SSTs.
Seasonal Trends and Long-Term Global Context
The Gulf of Maine is an area of particular interest to the scientific community because of the remarkable rate of warming it has experienced in recent years coupled with its importance as a major driver for the regional economy.
Figure 2 illustrates the average fall temperature anomaly for each year in the Gulf of Maine since the beginning of the satellite record in 1982 overlaid with long-term SST anomaly trends for the Gulf of Maine (orange) and global oceans (blue) overlaid.
The winter rate of warming for the Gulf of Maine (0.73°F per decade) is roughly ~3.3x as fast as the warming rate for oceans globally (0.22°F per decade).
The winter SST anomaly for the Gulf of Maine in 2024 was 4.29°F cooler than that from 2022, the largest year-over-year decline in winter temperatures in the satellite record.
Observed SSTs are influenced by atmospheric weather patterns which can act to amplify warming or cooling of surface waters. Sustained periods of low cloud cover and the consequent direct sunlight can rapidly warm the ocean at the surface. Steady winds can act as a fan, advecting heat away from the ocean and cooling the surface. Strong winds and storm systems may also lower SST through mixing, which can bring cooler water from depth closer to the surface.
Marine Heatwave Conditions
The most commonly used definition of a “marine heatwave” (MHW) is when daily average SSTs exceeded the 90th percentile of a climatological (i.e., 30-year) average for at least 5 consecutive days. Gaps of 2 days or less in this threshold do not constitute a break in the MHW event. Using this broadly accepted definition, the Gulf of Maine has experienced MHW conditions for 0% of days this winter.
Presenting SST conditions in terms of anomalies ( Figure 4 ) as opposed to absolute values ( Figure 3 ) illustrates in greater detail the magnitude of MHW conditions throughout the winter.
The highest daily SST anomalies for winter 2023-2024 occurred towards the end of December, with anomalies near 0°F above the climatological average. All daily SSTs after January 1st were below the climatological average, contributing to this season’s unexpectedly low ranking.
Heatmap of Temperature Anomalies and Heatwave Events
Looking at the full record of daily SST anomalies in the Gulf of Maine (Figure 5), the distinct thermal regime shift beginning around 2010 is evident. Indeed, since 2012, the Gulf of Maine has experienced far more persistent MHW conditions (indicated by solid black lines) than at any other point in the satellite record.
Winter SSTs in the previous 3 years had been noteworthy for their extended MHW conditions, part of the long-term trend of unseasonably warm fall since 2012 (Figure 2). The relatively cold winter in the Gulf of Maine this year were an extension of cooler fall conditions, but stand out against above-average winter conditions since 2012.
Spatial Distribution of Seasonal Anomalies
From an aerial perspective, the Gulf of Maine experienced below-average SSTs during winter of 2024. In general, conditions were cooler in the deeper-water basins and warmer in shallow protected areas like the Bay of Fundy and Massachusetts Bay. The highest seasonally averaged SST anomaly in the Gulf of Maine was 2.29°F - located near the Bay of Fundy.
Monthly Temperature Anomalies
Average monthly SST anomalies are shown in Figure 7.
About the Updates:
Over the past decade, scientists have led a body of research that highlights the rapid pace of warming in the Gulf of Maine. To help keep you informed, we share seasonal and annual updates about conditions in the Gulf of Maine.
Read on for an inside look at what we’ve learned in our winter 2023 Gulf of Maine warming update.
The Gulf of Maine Region
For analyses like these, it is important to be clear about the spatial extent that “defines” the Gulf of Maine (Figure 8), as different borders could produce different results. The spatial domain we use as the “Gulf of Maine” is displayed below. This area is consistent with previous seasonal and annual reports that scientists at GMRI have produced.
Data Sources:
NOAA High Resolution SST data provided by the NOAA/OAR/ESRL PSL, Boulder, Colorado, USA, from their Web site at https://psl.noaa.gov/data/gridded/data.noaa.oisst.v2.highres.html.
Citing This Work
If you would like to cite this report, please use:
Gulf of Maine Research Institute. 2024. Gulf of Maine Warming Update: Winter 2024
Note About the Data:
The figures in this report are created using remotely-sensed satellite data as part of publicly funded research efforts. Satellite SST data was obtained from NOAA’s National Center for Environmental Information (NCEI), with all maps and figures displaying NOAA’s Optimum Interpolation Sea Surface Temperature Data.
Note About the Data: The figures in this report are created using remotely-sensed satellite data as part of publicly funded research efforts. Satellite SST data was obtained from NOAA’s National Center for Environmental Information (NCEI), with all maps and figures displaying NOAA’s Optimum Interpolation Sea Surface Temperature Data.